Hydraulic hold-down



oct. 4, 1932. I R, -T HAZELTON I 1,881,185

HYDRAULI C HOLD -DOWN Filed Nov. z5. 1929 s sheets-shea 1 l E a @o le .2 Q a a :1 l v` I N V EN TOR.

ATTORNEY;

Oct. 4, 1932. v R, T, HAZELTON 1,881,185

HYDRAULI C HOLD -DOWN Filed Nov. 237 1929 3 Sheets-Sheet 2 INVENTQR.

mv BY f ATTORNEYJ" I BY @ma f V ATTORNEYS I Oct. 4, 1932. R` T HAZELTON 1,881,185

HYDRAULIC HOLD-DOWN Filed Nov. 23, 1929 5 Sheets-Sheet 3 INVENTOR.

25 oil. is left in the housing.

. l proofness which be *fnd relief chamber. i 45d Patented 4,

UNITED .STATES i mmm r;

PATENT- oFFlcs EAZELTON, F CHCINNATI, OHIO, SSIGNOB TO TBE mmm GQHIANY, 0F CINCINNATI, OHIO, A CQBPQBATION 0F Omo mam-.rue noLn-nown application mea lll-wennen as, laas. serial m.N 469,881.

My invention! relates to. hold-'downs or clamping devices, for use in retaining the work particularly in metal shears, but which l also be useful in other machine tools.

, It my object to provide a clamp for the work in shears and-the like which will en gage the work at a series of points, and in which the pressure against the work will be substantially uniform in spite of differences in thickness of the work, or in spite of varil ations in thickness when several kinds of work are being held down simultaneously.

It is my oblect to so provide that the hy? draulic system is operated by suitable master means suchas a. cam, in a praal-ranged timed relation to the operation ofthe tool. I also provide for aspring controlled relief and accumulator for the hydraulic system which is e vadjustable to control and maintain the def 2o' sired pressure `on the Work, and I further so connect the pump which applies the pressure with the accumulator and the housing in which it is located that the said pump will be effective as long as any substantlal amount of The mechanism itself which is employed has novel features in simplicity. and foolevident as the description proceeds. f Y :so I have illustrated my invention as applied to a wide shears, and will describe in full this one embodiment of m invention,`the novelty wherein Iv will set claims.

In the drawings: f Figure 1 is a perspective view ofa shears showing the clampin elements. v- Y I Fi re 2 is a det section through one of the c amping elements. j 4Q Figure 3 is a detail elevation partly in section of two ofthe clamping devices andthe 'connections therewith.-

Figure 4 is a detail section'of thev pump e 5 is a det il section on the line 5-5 of lFigure '4;

, Y jll It being understood that the particular `tylevosheanis.not of ortance 1n 'connec- Fleur Y tion with my invention, If aveshown a shear ha'ving housings 1, 1, a ram 2, and a bed 3.'

ders. This line is kept .full of oil, and presorth in the appended.

.is part of in which cylinder 1s the piston 16 (normally forced upward by a spring 17, so that the 'roller on the upper cam, which actuates vthe piston. The cylin- Thereis a bed plate 4 extendin'gnhorizontalli from the top of the bed ,3, on w ch the wor is supported when being acted upon by the blade of the shear. Y

A suitable support such as a metal Ychannel 5,- is supported from the housings of the machine, on lugs which in this case pass through slots in the ram, although this is not of impol-tance. p f. l

This channel serves to support a series of cylinders 6, in which arel l ted the pistons 7, said pistons held norma 1y upward in the cylinders by means of springs 8.

The rods 9 of the pistons are extended through the .lower ends of the cylinders, and serve as clamping or hold down elements to engage work located\ upon the bed plate 4. In the shear it is advisable to have the hold downs or clamping elements close to the cutting` line of the shear) blades.

The cylinders are connected at their upper ends to a common oil line formed of a pipe 10, together with the'ittings 10a connected thereto and to the upper ends of the cylinsure is applied bymeans of a pump to the oil to force the pistons to descend in the cylinders whereupon the piston rods will engage and hold down the work on the bed.

At the end of the channel is mounted a closed chamber 11, which serves as an oil reservoir'fr the vpump and in addition contains the pum and relief valve mechanism.

A sha 12 extends into this chamber said shaft being driven in synchronism wat the shaft which operates the shear ram. On this shaft is a cam 13, which engages a roller 14,

Ymounted on the top of the pump piston.

- The pum consists of a linder 15, which e pum and re 'ef valve casting,

end thereof follows the der 15 has a channel 16a onA its interior, 1ocated above the base of the housin 11, with ports -17 'therefrom'.into the cylin er, so as to supply oil to the walls of the cylinder, and seal the pump inst. air, as long as the oil level remains a ove the ports. Nor-v l@ mally the oilin the chamber will be held at oribove. the level of the top of theA pump cyl.- ln'llie pump cylinder is connected at 18 with 6; the. oilllineplpe 10, and is also connected through the passage 19 with a check valve 20. Thisfcheck valve consists of a ball marked 20, which closes a passage 21, said passage communicating withthe bottom of the chamber reservoir 11. When the piston in the pump moves upwardly it canv withdraw oil."

ton. The spring receiver 27 is held in place in the chamber by means of the rodsr 24 and is held down by nuts 28 threaded on the rods, said nuts being adjustable to control the force of the spring on the piston. Thus when the nuts are turned down the receiver 27 is forced down, thus placing the piston under greater tension. l The vent pipe 30 permits accumulated air together with some oil to seep back from the .'holdl down system to the reservoir. The needle valve 31 controls this air vent.

In the particular machine the timing of the cam which operates the pump piston is. .such that the clamping or hold down rods come into contact with the work before the shear blade becomes operative on the work.

Normally the 'reservoir 'will be filledwith oil to at least the top of the-pump piston. When the cam is rotated, and the pump piston thrust down, oil is placed under pressure in the several hold down or clamp cylinders, and as in hydraulic systems,- there will be equal pressure of `oil against the pistons in each of these cylinders irrespective-'of how far down the piston rods are permitted togo due to thev thickness of the work beneath them. The oil under pressureA is also present .in the accumulator or relief cylinder, and forces the piston therein upwardly against the compression of the spring. Thus the pressure will not be any greater-than suicient to raise the piston in the accumulator enough vto open the ports in the accumulator cylinder wall.` l p Moreover when the pump piston is released by .the cam, which' lwillv normally be a short period vprior to the raising of lthe shear blade, the accumulator piston is Well forced down by the spring supplying, in case of leakage in the clamping mechanism, additional oil. under the-prevailing pressure to maintain the a piston', means operated by the pistonA for 13 'clamping relation.

Should oil be required to kee the lines full at all times, thisA will be wi drawn by the pump piston kfrom the main reservoir through the check valve mechanism described.

the purposes required.. Such a mechanism c willu be of use also'in 'other machines particularly where a wide bed is provided, and on which work of differing thicknesses, and

requiring varying pressures is to be emv ploy-d.

Having'thus described my invention, what I claim as new and desire to secure by Letters Patent, is

1. In a machine tool the combination with 'a bed of means to hold work down on the bed comprising a series of interspaced hydraulic Cylinders with pistons, members operated by the pistons for engaging the work on the bed, and a pump for placing the luid insaid cylinders under-pressure, and means operated in timed relation with the machine tool mechanism for operating said pump.

2. In a metal shears, the combination with a bed .of means to hold work downy on said bed comprising a series of hydraulic hold downmembers spaced from each other, land common means for placing said hold down means into movement and under pressure, comprising a master cylinder and piston, the system so arranged that movement of the piston 4in one direction moves the hold down members to work holding position, and movement-of the piston in the opposite direction releases said members.

3. In a metal shears, the combination with a bed of means to hold work down on the bed comprising a series of interspaced hydraulic cylinders with pistons, members operated by the pistons for engaging the work on the bed,-

and a pump for placing the fluid'in, said cylinders under pressure, comprising a mastery cylinder and piston, vthe system so arranged that movement of the piston in one direction moves the hold down members to work holding position, and movement of the piston in the opposite direction releases said members. 4. vIn a hydraulic hold down mechanismfor machine` tools the combination with a series of hydraulic clampin members of a device for placing said mem rs under compression comprising a pump, an accumulator vconnected to said ump and having suicient .power tov maintain the "maximuml required compression on said clamping members.

5.v In a machine tool the combination with a bed of means tohold work'down on the bed comprising a. hydraulic cylinder having l engaging work on the bed, a. pump. flor-Icompressing the iiuid in said cylinder an'dfliieans operated in timed relation with the machine tool mechanism for operating said pump.

6. In a .hydraulic hold-down mechanism the combination with a series of hydraulic clamping -members, a pump for operating the same having a reciprocating piston arranged so lthat movement in one direction will apply the clamps and a reverse movement will release' the clamps, an accumulator connected to' said pump andhaving a port disclosed when the hydraulic pressure created by thepump reaches the required value.

7. In a machine tool the combination with a bed, of means to hold work down on the bed comprising a series of. interspaced hydraulic cylinders with pistons, members operated by the pistons 'for engaging the work on the bed, a pump for placing fluid in said cylinders under pressure, comprising a'piston so arranged as to place said cylinders under pressure to make an application of Work engaging members upon the movement of said piston in one direction and to release the said members upon movement of the piston in the opposite direction, means operated in timed relation with the machine tool mechanism for operating said piston, and a relief valve in said system for the purpose described.

8. In a machine tool the combination with a bed, of means to hold work down on the bed comprising a series of inters'paced hydraulic cylinders with pistons, members operated by the pistons for engaging the work on the bed, a pump for placing uid in said cylinders under pressure, comprising a iston so arranged as to place said cylin ers under pressure to make an application of work engaging members upon the movement of said piston in one direction and to release the said members upon .movement of the piston in the opposite direction, means operated in timed relation with the machine tool mechanism for operating said piston,

and a combined accumulator and relief valve in said system.

9. In a machine tool, the combinationwith a bed,'of means to hold work down on said bed comprising a series of hydraulic holddown members spaced from each other, a

Apump for placinthe fluid in said hydraulic hold-down mem ers under pressure, and means operated in timed relation with the machine tool mechanism for operating said Pump` l ROBERT T. HAZELTQN. 

